ON VOLUNTARY MOVEMENTS. 



663 



tongue, and so on. Obviously in the dog this region of the cortex has con- 

 nections with the skeletal muscles which do not obtain between other regions 

 of the cortex and those muscles ; and further, the region in question is topo- 

 graphically differentiated, so that certain areas or districts of this region are 

 specially connected with certain skeletal muscles or groups of muscles. We 

 may speak of a " localization of function " in this region as compared with 



FIG. 147. 



The Areas of the Cerebral Convolutions of the Dog, according to Hitzig and Fritsch. (1) B, 

 The area for the muscles of the neck. (2) A, The area for the extension and adduction of the 

 fore limb. (4) E, The area for the flexion and rotation of the fore limb. (4) C, The area for the 

 hind limb. Running transversely toward and separating 1 and 2 from 3 and 4 is seen the crucial 

 sulcus, (5) D, The facial area. 



other regions of the cortex, and in the several areas within the region as 

 compared with each other. 



The muscles which are thus thrown into contraction are the muscles of 

 the opposite side of the body. When " the fore-limb area," as we may call 

 it, of the right hemisphere is stimulated, it is the left fore limb which is 

 moved; and so with the other areas; it is only in exceptional cases, as in 

 certain movements of the eyes, that the effect is bilateral ; a movement 

 confined to the same side as that stimulated is never witnessed. 



The results are most clear when the current employed as a stimulus is not 

 stronger than is just sufficient to produce the appropriate movement (roughly 

 speaking, a current just perceptible to the tongue of the operator is in ordi- 

 nary cases a useful one), and when the cortex is in good nutritive condition. 

 In any experiment the results obtained by the earlier stimulations, soon after 

 the cortex has been exposed, are the best ; after repeated stimulations the 

 surface is apt to become hyperamic, and it is then frequently observed that 

 the movements resulting from the stimulation of a particular area are not 

 confined to the appropriate muscles, but spread to the corresponding muscles 

 of the opposite side, then to muscles connected with other cortical areas, and 

 at last to the muscles of the body generally ; at the same time the move- 

 ments lose their distinctive purposeful character and the animal is thrown 

 into convulsions of an epileptiform kind. It not unfrequently happens that 

 an experiment has to be stopped in consequence of the onset of these epilep- 

 tiform convulsions. The response of movement to stimulation may be ob- 

 served while the animal is under the moderate influence of an anaesthetic, 

 but a too profound anaesthesia lessens or annuls the effects. 



